Monthly Archives: July 2018

At the least, wastewater from oil and gas drilling should be treated in a waste treatment facility before it is used on dirt roads to suppress dust or deice roads. At the best, affordable, nontoxic dust suppressants should be developed and used, according to a multidisciplinary team of researchers.

“Thirteen states in the United States have regulations that allow oil and gas wastewaters to be spread on roads for deicing or dust suppression,” the researchers report today in Environmental Science & Technology.

The team analyzed regulations across the U.S. to determine where this wastewater can be used for dust suppression and deicing. While 13 states have regulations that permit its use, other states may allow wastewater spreading on roads under their land spreading regulations, which could mean four additional states may be included among those that use the wastewater.

The wastewater in question comes from conventional oil and gas wells that are typically drilled vertically. The wastewater is not the fluid used in directionally drilled and hydraulically fractured wells, such as the Marcellus wells.

“Oil and gas wastewaters are known to have high salt, organic and radioactivity concentrations,” said Travis L. Tasker, graduate student in environmental engineering, Penn State. “When we found out that this wastewater was being spread on roads, we wanted to evaluate its potential to cause biological toxicity and accumulate in road material or migrate into water resources.”

Analysis of oil and gas wastewater shows that it has a high salt content containing sodium, calcium, magnesium and strontium, which may make it ideal for dust suppression and deicing.

“We would like to do experiments to test how effective the wastewaters are at suppressing dust in comparison to other commercial products,” said Nathaniel R. Warner, assistant professor of environmental engineering, Penn State. “If the salts in the wastewaters are just as effective, then new regulations or additional treatment prior to spreading could help reduce the concentration of other contaminants of concern that exist in wastewaters, but not in commercial products.”

These other contaminants of concern may include radium or other micropollutants the team found in wastewaters spread on Pennsylvania roads.

“Radium is known to cause cancer, so we are concerned if it is spread on roads in high concentrations,” said William D. Burgos, professor of environmental engineering, Penn State.

The researchers collected wastewaters from townships in Pennsylvania that spread wastewaters and did simulated lab experiments to see where the contaminants in the wastewater end up. They found that the salts wash off in subsequent rain, but that some of the metal contaminants, such as lead, remain on the road surface and are not washed off. Some of the radium stays in the road, but some of it washes off in rain events.

While organic materials, radium and heavy metals can all be a problem in the wastewater, another problem with the mixture is high salt. Conventional wastewater treatment can remove some of the contaminants, but it cannot remove or lower the salt concentration. If oil and gas wastewater were to be used as a dust suppressant or deicer, the researchers suggest that at a minimum, wastewater treatment should be used to remove organics and radium beforehand.

Although the researchers recommend that alternative, inexpensive material be developed to replace the oil and gas wastewater in places where it is used, they understand that many of these places cannot afford currently available alternatives. Municipalities would be faced with either using the wastewater, or not deicing or suppressing dust.

Engineers use byproduct from coal-fired power plants to replace Portland cement

Rice University engineers have developed a composite binder made primarily of fly ash, a byproduct of coal-fired power plants, that can replace Portland cement in concrete.

The material is cementless and environmentally friendly, according to Rice materials scientist Rouzbeh Shahsavari, who developed it with graduate student Sung Hoon Hwang.

Fly ash binder does not require the high-temperature processing of Portland cement, yet tests showed it has the same compressive strength after seven days of curing. It also requires only a small fraction of the sodium-based activation chemicals used to harden Portland cement.

The results are reported in the Journal of the American Ceramic Society.

More than 20 billion tons of concrete are produced around the world every year in a manufacturing process that contributes 5 to 10 percent of carbon dioxide to global emissions, surpassed only by transportation and energy as the largest producers of the greenhouse gas.

Manufacturers often use a small amount of silicon- and aluminum-rich fly ash as a supplement to Portland cement in concrete. “The industry typically mixes 5 to 20 percent fly ash into cement to make it green, but a significant portion of the mix is still cement,” said Shahsavari, an assistant professor of civil and environmental engineering and of materials science and nanoengineering.

Previous attempts to entirely replace Portland cement with a fly ash compound required large amounts of expensive sodium-based activators that negate the environmental benefits, he said. “And in the end it was more expensive than cement,” he said.

The researchers used Taguchi analysis, a statistical method developed to narrow the large phase space — all the possible states — of a chemical composition, followed by computational optimization to identify the best mixing strategies.

This greatly improved the structural and mechanical qualities of the synthesized composites, Shahsavari said, and led to an optimal balance of calcium-rich fly ash, nanosilica and calcium oxide with less than 5 percent of a sodium-based activator.

“A majority of past works focused on so-called type F fly ash, which is derived from burning anthracite or bituminous coals in power plants and has low calcium content,” Shahsavari said. “But globally, there are significant sources of lower grade coal such as lignite or sub-bituminous coals. Burning them results in high-calcium, or type C, fly ash, which has been more difficult to activate.

“Our work provides a viable path for efficient and cost-effective activation of this type of high-calcium fly ash, paving the path for the environmentally responsible manufacture of concrete. Future work will assess such properties as long-term behavior, shrinkage and durability.”

Shahsavari suggested the same strategy could be used to turn other industrial waste, such as blast furnace slag and rice hulls, into environmentally friendly cementitious materials without the use of cement.

New coal concrete reduces energy demand, greenhouse emissions

Washington State University researchers have created a sustainable alternative to traditional concrete using coal fly ash, a waste product of coal-based electricity generation.

The advance tackles two major environmental problems at once by making use of coal production waste and by significantly reducing the environmental impact of concrete production.

Xianming Shi, associate professor in WSU’s Department of Civil and Environmental Engineering, and graduate student Gang Xu, have developed a strong, durable concrete that uses fly ash as a binder and eliminates the use of environmentally intensive cement. They report on their work in the August issue of the journal, Fuel.

Reduces energy demand, greenhouse emissions

Production of traditional concrete, which is made by combining cement with sand and gravel, contributes between five and eight percent of greenhouse gas emissions worldwide. That’s because cement, the key ingredient in concrete, requires high temperatures and a tremendous amount of energy to produce.

Fly ash, the material that remains after coal dust is burned, meanwhile has become a significant waste management issue in the United States. More than 50 percent of fly ash ends up in landfills, where it can easily leach into the nearby environment.

While some researchers have used fly ash in concrete, they haven’t been able to eliminate the intense heating methods that are traditionally needed to make a strong material.

“Our production method does not require heating or the use of any cement,” said Xu.

Molecular engineering

This work is also significant because the researchers are using nano-sized materials to engineer concrete at the molecular level.

“To sustainably advance the construction industry, we need to utilize the ‘bottom-up’ capability of nanomaterials,” said Shi.

The team used graphene oxide, a recently discovered nanomaterial, to manipulate the reaction of fly ash with water and turn the activated fly ash into a strong cement-like material. The graphene oxide rearranges atoms and molecules in a solution of fly ash and chemical activators like sodium silicate and calcium oxide. The process creates a calcium-aluminate-silicate-hydrate molecule chain with strongly bonded atoms that form an inorganic polymer network more durable than (hydrated) cement.

Aids groundwater, mitigates flooding

The team designed the fly ash concrete to be pervious, which means water can pass through it to replenish groundwater and to mitigate flooding potential.

Researchers have demonstrated the strength and behavior of the material in test plots on the WSU campus under a variety of load and temperature conditions. They are still conducting infiltration tests and gathering data using sensors buried under the concrete. They eventually hope to commercialize the patented technology.

“After further testing, we would like to build some structures with this concrete to serve as a proof of concept,” said Xu.

The research was funded by the U.S. Department of Transportation’s University Transportation Centers and the WSU Office of Commercialization